New mobile telephone communication standards have been defined. The standards such as Long Term Evolution (LTE) and LTE-Advanced, and a set of standards for the fourth generation of mobile telephones (4G) have been developed by the Third Generation Partnership Project (3GPP), which is a standardization organization, and the International Telecommunication Union (ITU) respectively. It is expected in these standards that frequencies ranging from a few 100 MHz to about 3.5 GHz will be used. Furthermore, when the Worldwide Interoperability for Microwave Access (WiMAX) or wireless local area network (LAN) function is to be included in wireless terminals in the future, antennas to be included in the terminals may transmit and receive electromagnetic waves with a frequency of about 6 GHz.
The antennas of mobile telephones are primarily required to be small. Secondly, the antennas are required to have a higher capability to be able to handle multiple frequency bands over a wide frequency range. Various antennas for the purpose of use in multiple frequency bands are proposed. Japanese Laid-open Patent Publication No. 2007-300398 discloses an antenna configured as illustrated in FIG. 9. The antenna is a monopole antenna with multiple arms 214 and 216 connecting with a radiating element 212 via branching portions 213 and 215, where reference numerals 210 and 211 are a circuit board and a feeding point respectively. The individual arms 214 and 216 have different resonant frequencies each other.
Further, Japanese Laid-open Patent Publication No. 2000-124728 discloses an antenna configured as illustrated in FIG. 10. The antenna has been disclosed as conventional multi-frequency antenna, where the antenna includes a tabular conductor 316, capacitances 317, a feeding point 318, switches 319, and an excitation source 321 on a virtual ground plane 300. This antenna is a loop antenna that may select one of multiple impedances by using switches 319.